I think the explanation is quite simple. The bits of Deming that is easy to boil down into a course you can systematise delivery of and charge through the nose

I think the explanation is quite simple. The bits of Deming that is easy to boil down into a course you can systematise delivery of and charge through the nose for verification are exactly the bits that look most Taylorist. And when you're selling into a business environment where most management believes in Taylorism, that both makes it easy to sell and easy to buy into selectively. What you end up with is bias confirmation: the existing managers think they're buying a system that lets them do what they were already doing more effectively (because what they were doing didn't work very well), and there's enough group-think in the peer group that nobody notices their entire philosophy is being challenged.